package com.uprizer.free.bloom;

import java.text.DecimalFormat;
import java.util.HashSet;
import java.util.Random;

import junit.framework.TestCase;

/**
 * This code may be used, modified, and redistributed provided that the author
 * tag below remains intact.
 * 
 * @author Ian Clarke <ian@uprizer.com>
 */

public class SimpleBloomFilterTest extends TestCase {
	public static void main(String[] demo) {

		DecimalFormat df = new DecimalFormat("0.00000000000000");
		for (int x=1; x<100; x*=2) {
		SimpleBloomFilter<String> mammals = new SimpleBloomFilter<String>(x*100,
				100);
		System.out.println("<tr><td>1:"+x+"</td><td>"+df.format(mammals.expectedFalsePositiveProbability())+"</td></tr>");
		}
	}

	public void testBloomFilter() {
		DecimalFormat df = new DecimalFormat("0.00000");
		Random r = new Random(124445l);
		int bfSize = 400000;
		System.out.println("Testing " + bfSize + " bit SimpleBloomFilter");
		for (int i = 5; i < 10; i++) {
			int addCount = 10000 * (i + 1);
			SimpleBloomFilter<Integer> bf = new SimpleBloomFilter<Integer>(
					bfSize, addCount);
			HashSet<Integer> added = new HashSet<Integer>();
			for (int x = 0; x < addCount; x++) {
				int num = r.nextInt();
				added.add(num);
			}
			bf.addAll(added);
			assertTrue("Assert that there are no false negatives", bf
					.containsAll(added));

			int falsePositives = 0;
			for (int x = 0; x < addCount; x++) {
				int num = r.nextInt();

				// Ensure that this random number hasn't been added already
				if (added.contains(num)) {
					continue;
				}

				// If necessary, record a false positive
				if (bf.contains(num)) {
					falsePositives++;
				}
			}
			double expectedFP = bf.expectedFalsePositiveProbability();
			double actualFP = (double) falsePositives / (double) addCount;
			System.out.println("Got " + falsePositives
					+ " false positives out of " + addCount
					+ " added items, rate = " + df.format(actualFP)
					+ ", expected = " + df.format(expectedFP));
			double ratio = expectedFP / actualFP;
			assertTrue(
					"Assert that the actual false positive rate doesn't deviate by more than 10% from what was predicted",
					ratio > 0.9 && ratio < 1.1);
		}
	}

}
